It is known that panels are present, under the dashboard of motor vehicles, having as their main function that of reducing the transmission of noise emitted under the dashboard towards the rest of the passenger compartment, for example by the motor-driven fan unit of the air-conditioning.
The installations for motor-vehicle heating and/or air-conditioning furthermore require air-diffusion ducts to be put in place, which are housed especially in the dashboard, for the front passengers.
However, the ducts are generators of airstream noise since, on the one hand, they receive an airflow generated by the air blower and therefore propagate the vibration from it, and, on the other hand, they exhibit an extremely large surface area through which the noises originating from the blower and/or from the simple flowing of the air can be propagated.
One object of the invention is to reduce the noise generated by the air ducts.
Another object of the invention is to achieve this noise reduction without complicating the manufacture of the duct or ducts.
Another object of the invention is to improve passenger comfort, especially for the front passengers, by improving the diffusion of the air.
The invention thus relates to an air-diffusion panel for a motor vehicle including at least one air inlet and at least one air duct in communication with the said air inlet and means for air distribution, particularly towards the feet of at least one passenger, characterised in that it includes at least one resonant cavity tuned so as at least partially to reduce the airstream noise in the said duct.
The device according to the invention can be used for diffusion on another surface of the passenger compartment, for example the roof, at least one door and/or at least one lengthwise member, possibly with the application of a decorative trim to the outside, for example by hot application by thermoforming of a bonded fabric, which does not stop up the air-diffusion orifices.
At least one air duct may feature outlets consisting of apertures opening out in at least one panel face.
At least one resonant cavity can be tuned in such a way as at least partially to reduce the noises passing through the said panel. These noises have an airstream origin specific to the duct, or else arise from a different origin, for example from under the dashboard.
The number and the size of the apertures can be configured for a low-speed air diffusion (called xe2x80x9cgentlexe2x80x9d diffusion), which makes it possible to diffuse air especially towards the passengers""feet without the air speed inducing a direct sensation of heat or of cold.
At least one resonant cavity can be closed.
It may lie alongside an air duct. It may extend between two air ducts.
The panel advantageously includes at least one resonant cavity which opens out into at least one air duct.
The panel may be single-piece, made of thermoplastic material, and be produced by extrusion blow-moulding, for example like the panel described in the French Patent Application No. 98 05397 filed on Apr. 9, 1998 by the Applicant Company and having the title of xe2x80x9cMotor-vehicle dashboard panelxe2x80x9d.
The panel can be produced by thermoforming.